Heretofore, some methods have been known for the production of dimethyl ether from a mixed gas composed of carbon monoxide, carbon dioxide and hydrogen.
For example, Japanese Patent KOKOKU 54-32764 discloses a method of producing dimethyl ether by loading a mixture of a methanol synthesis catalyst made of copper carried on alumina and a methanol dehydration catalyst made of zinc and chromium carried on alumina into a reactor or loading them into layers alternately into a reactor and supplying a mixed gas composed of carbon monoxide, carbon dioxide and hydrogen thereto. Besides, Japanese Patent KOKOKU 61-43332 discloses a method of producing dimethyl ether using a catalyst composed of a mixture of oxides of copper, zinc, chromium and aluminum treated with a silicon compound such as tetraethyl orthosilicate so as to resist heat, high temperature stream and mechanical stress and then molded. Moreover, Japanese Patent KOKAI 3-181435 discloses a method of producing dimethyl ether characteristic in the use of a catalyst in a slurry state formed by suspending in a solvent, in a method of producing dimethyl ether from a mixed gas of carbon monoxide and hydrogen or a mixed gas them further containing carbon dioxide and/or water vapor.
The above conventional method of producing dimethyl ether had some problems as follows:
As to the catalyst composed of oxides of copper, zinc, chromium and aluminum, the mechanical strength of catalyst particles is insufficient and the catalyst particles are gradually powdered by the action of gas fluid, heat, etc. which pass through the catalyst layer at a high speed resulting in the occurrence of clogging of the catalyst layer.
Besides, it was also a problem that the water by-produced at the time of producing dimethyl ether from methanol reacts with the oxides of aluminum to degrade the strength.
Moreover, since the catalytic activity of the catalyst is gradually decreased with the passage of reaction time, when the catalytic activity is decreased, it is necessary to be regenerated. Accordingly, the catalyst must be taken out from the reactor and then regenerated. However, it was especially troublesome to take out the catalyst.
Furthermore, since the method of synthesizing dimethyl ether from carbon monoxide and hydrogen is an extremely great exothermic reaction, the method had a problem that partial heating is liable to occur and it is not easy to maintain and control the reaction temperature uniform.
The present invention has been made in order to solve the above mentioned problems of the prior art and further to improve the method described in Japanese Patent KOKAI 3-181435 which the inventors previously developed, and an object of the invention is to provide a method of producing dimethyl ether wherein, mechanical strength is not required for the catalyst, taking out and regeneration of the catalyst are easy, and the removal of reaction heat and the control of reaction temperature are also easy.